Castiel the Avenger
by RandomHamster33
Summary: Castiel is trying to warn Sam and Dean. About what, he has no clue. And that's bad.
1. Warning

Sam and Dean stopped, hearing the familiar rustle of wings behind them. They turned around.

Castiel stood still as he always did. His eyes searched the brothers with soulful purpose, expression blank.

"Hello, Dean, Sam," Castiel said, a nod of his head at each brother. He took a step forward. "I've come to warn you."

Dean narrowed his eyes. "What? Warn us of what?" He approached Castiel, reaching out to him. "Cas, what's wrong?"

Castiel blinked. "I don't know."

"You don't know? What do you mean, 'you don't know?'" Dean grabbed Castiel's arm tightly, causing the angel to look down at the grip on him. He just stared at it.

"Cas? What's going on?" Sam asked. He walked up and stood next to Dean.

"I don't know. There's something coming. Something dangerous. I can't tell what it is, but it's huge. You need to be prepared," Castiel murmured. He looked up and into Dean's eyes. "It's angry. And it knows. But what it knows, I'm not sure. I can sense it." Suddenly, the angel grimaced, legs failing him as he fell to the floor in a daze. His eyes squeezed shut, nose wrinkled as Dean caught him halfway through his fall. Castiel gasped, eyes flying wide open. He grasped Dean's arms, trying to stand up but failing.

"Cas! Cas! Can you hear me?" Dean yelled, shaking the angel.

"D-Dean, you have to get out of here. Leave. Just leave. I don't want you to get hurt." Castiel felt his legs give out completely. He fell to the ground, Dean so unprepared for the sudden weight that he nearly fell over as well. The angel lay unmoving in the dirt. Dean got onto his knees and shook him violently, gripping the lapels on his coat.

"Sam, don't just stand there! Help me!" Dean snapped as he tried to pull Castiel up. Sam jerked into action and went around to Castiel's head, taking him under the arms while Dean grabbed his legs. Together, they moved the angel to the Impala that sat about twenty yards away. Dean opened the back door and they maneuvered Castiel so he was laying on the seats.

"What. . what just happened?" Sam asked, staring at the angel laying limply in the back of their car.

"I don't even know," Dean muttered. He crossed his arms and leaned on the Impala. "And apparently, neither did Cas!"

"Whatever's coming is big news. We need to find out."

"From who? If Cas didn't even know, then who would?"

Sam gazed at his brother. "Then what do we do?"

"We'll have to wait until Cas is better." Dean glanced down at the unconscious angel. He bent down and gave Castiel's foot a quick shake. With a gasp, Castiel shot up, shocking both brothers nearly out of their skin.

"I have to- I have to go!" Castiel shouted. Before any of them could say otherwise, the angel vanished on the spot. He left only a deep red stain covering the place where he laid.

* * *

The agents on the helicarrier were working steadily. Clicking of computer keys and shoes walking across the polished floor of the ship were accompanied by voices talking and yelling. The roar of the engines buzzed dully in the background. It was only when a bloody man appeared right in the middle of the room and fell unconscious that the yelling increased. Workers stopped what they were doing and rushed forward. The voices were fading together in a blur, yells increasing in volume echoing throughout the room.

A man walked in, one eye covered by an eye patch. He was accompanied by a woman with brown hair. "What's going on?" Fury demanded, stomping down the stairs towards the crowd of people.

"He just appeared, sir, then fell unconscious," a man replied. Fury narrowed his eye and pushed his way through the people, who quickly stepped off.

Dropping down to one knee, Fury checked the man for a pulse. "He's alive. Get him to the infirmary!" At once, agents came through with a stretcher and transferred him to it, then rushed off.

* * *

"He just appeared? That's what his story is?" Agent Romanoff asked as the trio walked down the hall.

"Yeah, I guess. Wherever this guy came from, I don't trust him. Might be working for Loki," Fury said.

"Is he awake yet?"

"No. And the reason I brought you to see him is that his blood was tested and the information came back as 'undefinable.'"

"Alien?"

"Most likely," Agent Hill added in from the opposite side of Fury.

"Interesting. Should I tell the others, or. .?"

"Don't. Not until we find out what this guy is," Fury said. As he finished his sentence, he pushed open the doors to the hospital area of the helicarrier. The trio walked down the hall, passing a few doctors and nurses along the way. At the end of the hall was a door, which was currently housing the interesting man.

"Hello, Director Fury. Here to see the patient?" a woman asked.

"Yes, we are," Fury replied.

"Well, good, because he just woke up."

* * *

**Hiyah people! Yes, this is another Avengers crossover fanfic. For those of you waiting for Blue skies and Blue Boxes, don't fret. The updates on this story probably won't consume all my time and effort. I'm working. While I'm watching Supernatural. So. . . yeah. Great show. I love Castiel. Btw, this is set somewhere in season 5? Before he became God, anyways. **


	2. Infirmary

Castiel slowly opened his eyes. His head pounded for a few moments before calming down. He looked around.

At once, the angel shot up in the bed he was in. Castiel groped at the blankets, trying to throw them off. But before he could, hands came down on his arms, pinning him to the bed.

_My powers must have burned out in whatever happened_, Castiel thought as he was fairly easily restrained. Now with leather straps wrapped around his arms and legs, keeping him attached firmly to the bed, he looked around with a bit more focus. He was currently in some sort of room. A few women and men stood around his bed, apparently the ones who had restrained him. White walls and floor. Pretty much white everything.

"Hello, sir. Don't panic, we just needed to restrain you because of protocol," a tall woman said from in front of Castiel. She had a customary white hospital uniform on. SHIELD was written across the left half of her chest in black. Her light brown hair was curled, naturally, he could tell, and it ran down her back to about the middle of it. She stepped forward so she was closer.

"I'm Doctor Sandvik. I'm the head doctor here. I'm with the agency SHIELD. I can't explain much, but there's someone coming to see you. He won't hurt you, okay?" she assured, nodding her head. Castiel narrowed his eyes slightly, still keeping the look of absolute bewilderment on his face.

"I'm not a child. I'm not afraid of you," the angel said back, somewhat coldly.

Doctor Sandvik gave a small smile. "I never said that you were." She patted his hand that was resting on the bed and then stood up. She exited the room and vanished down the hall. The other nurses and doctors left the room also, so when they came back they'd be alone.

As Castiel stared at the ceiling (which was a slightly darker shade of white, he noticed), the door opening caught his attention. Castiel turned his head towards it.

A man with an eyepatch entered, followed by two women. Castiel narrowed his eyes at them. Doctor Sandvik was the last inside. She quickly closed the door and stood by Castiel's bed.

"Director. Here he is. As protocol intended, I have not asked any questions," Sandvik announced formally.

"Thank you. If you'll get the blood results, please," Fury responded. Sandvik shifted towards Fury slightly and whispered to him:

"We found something else quite interesting just as he was waking."

Fury raised his eyebrows. As he gave her an allowing nod, Doctor Sandvik went off into a different side room. When she was gone, Fury and the two woman looked at Castiel. After a few moments of intense staring on both ends, someone finally spoke.

"Where am I?" Castiel asked, tilting his head.

"On a helicarrier somewhere above the United States," Fury replied somewhat snappily. He then took a step forward. "And for the remainder of the time, I'll be asking the questions."

"Well, okay then."

"First of all, I'm Nick Fury. I'm in charge of this operation."

"We're doing surgery? I don't think I need it. Besides, that other doctor seemed like she knew what she was doing."

"Don't get smart with me!" Fury slammed his hand down on the small table next to the bed. Castiel didn't jump or flinch, but just stared.

Natasha tapped Fury on the shoulder lightly, then moved in front of him. "I'm Agent Romanoff."

"Agent Hill," came the other woman's voice.

Castiel nodded. There was a moment of silence. Fury sighed.

"Identify yourself," the Director stated firmly.

"Castiel," the angel said simply. Recalling what Dean said about not telling them the whole truth, like the fact he was an angel, but twisting his answers, he made sure not to say anything else.

"Interesting name. Never heard that one before," Natasha said.

"Now you have."

The Agent smirked, looking at Fury and Hill. "Isn't that great."

After she said that, the door opened to the left and Doctor Sandvik entered, holding an X-Ray and a different sheet of paper. She handed both to Fury. He studied them and then held them both up for Castiel to see.

"And what do you call these?" Director Fury asked. The X-Ray was of Castiel's rib cage. Enochian and other symbols were carved into them, on every single bone, like Sam and Dean's. The other had his blood test results. On the bottom of the page, in bold black letters, were the words: Blood Belongs To: Unidentifiable. The angel stayed silent.

"I said, what are these?!" Fury shouted again, getting closer into Castiel's face.

"They're test results and an X-Ray," he answered the angry man.

"Do you have a death wish?"

"Not really." Castiel blinked.

Taking a deep breath, trying to not lose his cool. "You see, Castiel, here's how it's going to work: you're going to tell us what we want to know, and you might get off without getting mortally wounded. Now, I suggest you start talking. Because if we hadn't had to bring you to the infirmary, you'd be strapped to a torturing table instead of a hospital bed. Get the picture?"

Castiel tilted his head. "And how would you torture me?"

Without warning, Fury's fist hit Castiel straight in the face, knocking his head back. Fury took his fist back, looking down with a small grimace at the blood covering his knuckles. Yet Castiel's face was clean as it was a moment ago.

"I don't think that's going to work for you," the angel said plainly. "And can I be unstrapped from this bed now?"

"You can be unstrapped as soon as you tell me what you are and why you're here," Fury growled.

"Dean says I'm not supposed to tell you."

"And who is this Dean?"

"My friend."

"Is he a freak too?"

"Well, he's not normal, if that's what you're asking. He's been to Hell and back. And Heaven. And Sam too. And me. All of us. I saved them both from Hell. I pulled them out with my own hands."

Agent Romanoff leaned over and whispered into Fury's ear: "I think we should interrogate him somewhere else. He doesn't really look that bad."

"Of course I don't look that bad. I've already started healing, hence the punch not working," Castiel informed them. He pulled at his bindings slightly. "I can rip these off if I try."

Fury placed his hands on his hips, cocking in eyebrow. "Oh yeah? Well, how about you show us."

Agent Hill gave Fury a worried glance. "Sir, I'm not sure that's the best idea-"

"Nonsense." He waved a hand at her. "Let's see if this guy is as formidable as he says he is." He turned his attention back to Castiel. "Give it a try."

Castiel looked at the four people before looking back down at his restraints. He clenched his fists and focused, closing his eyes. Since his strength was not all back, it'd take some effort. His muscles strained as he worked with his mind and his body. He could still feel the others in the room staring at him; observing his actions. In only a matter of a few minutes, the straps containing him loosened and with a final, hard pull, they ripped from the bed and snapped in different pieces, being strewn across the room.

"Well well well," Fury said, impressed, "looks like you could do it. Since you seem to be in better health, I think it's time for a little interrogation session, don't you, ladies?" He glanced around at the females. They met his gaze and just by the looks on their faces, he could tell.

Fury clapped his hands together. "Alright then! If you'd call security, Doctor Sandvik?"

* * *

**Sorry for the wait. I just could not get this chapter right. It still seems awkward. :/**


	3. I am an Angel of The Lord

"Unhand me!" Castiel snapped angrily as the guards grabbed him by the arms and started to drag him off. The angel struggled violently, managing to break free from the hands around him a few times before they shocked him with a tazor, stunning him enough to lead him away.

Castiel was half-dragged half-walked out of the room and down the halls. Several twists and turns later, they were at a small interrogation room, which the angel was shoved in, rather roughly, too. He was forced down into a metal chair, then handcuffed to the table in front of him. Castiel looked down at the restraint on his wrist, his face expressionless. Then, with a small yank, he ripped the cuff off, away from the table, freeing himself.

A guard, who was standing nearby, quickly called for something stronger and they delivered. A metal collar was fastened around Castiel's neck, which was attached to thick pieces of metal around his wrists. Another two chains were fixed to the ground, in special ports for holding them.

Grunting, Castiel attempted to pull them off, but he wasn't strong enough for that yet. These were much stronger than the measly little handcuffs he'd had on only a few minutes ago. He sighed.

He was now trapped in a twenty-by-twenty foot concrete room. There were no windows. There was only the chair and table, the door, and most likely some cameras watching him.

Castiel was only sitting there for about three minutes when Fury walked in. He seemed fairly angry.

"So," Fury started, planting his feet firmly right in front of the table. "What are you, Castiel? Where are you from?"

The angel didn't say anything.

"Giving me the silent treatment?"

"What will happen to me if I do tell you?" Castiel asked, wanting to know. Once his strength returned enough so he could fly off, that's what he'd do. But he needed to find out what was happening. . it felt so _unholy_. He had to find out was occurring here.

"Depends."

"Because if I do tell you, most likely nothing would happen. Only those who have knowledge of what I am and my species can hurt me. You don't have the tools." Castiel locked eyes with the Director, his gaze intense.

"I wouldn't say we don't, but I won't say we do." Fury placed his hands on the table. "And if we do find out what you are, we will find any means necessary to do what we have to do."

"I assure, I am no threat. I help the human race. I have friends who can say so."

"Then why don't you tell us where these friends are?" Fury asked.

"I would never tell you. I don't trust you," Castiel said.

"I can understand that."

Castiel didn't reply right away. Instead, he contemplated his next words carefully. "I have a question."

"What's that?"

"Is there something going on? I sensed something. It. . ." Castiel trailed off. "It was so bad it caused me to break. Something so unholy that I ended up here. I just can't tell what it is."

Fury looked shocked for a moment. "What?" He leaned in closer to Castiel. "What do you know about what's happening?"

No stranger to having people close to his face, Fury's intense glare did nothing to him. "I don't know anything. All I know is that it's something bad. And I'd like to help. I'm already in the middle of a war. I don't want another one."

"You'd like to help?" Fury laughed. "What could you possibly do?"

"You've already seen some of what I can do. And I'm not even at half strength yet," Castiel stated. "I'm still healing from the initial shock of it. Something this bad has had a certain _toll_ on me."

Fury thought it over. True, they needed more people to fight. They'd already lost Loki, gotten the helicarrier blown up, Thor and Banner lost somewhere, and were most likely on the losing side of this fight. But if this Castiel wanted to help, then Fury wanted to know what in the hell he was.

"If I consider, you need to tell me what you are. I can't even begin to trust you if you keep your identity a secret," Fury said.

Castiel thought it over. If he'd be able to help, he needed to tell them who and what he was. "Just don't panic when I tell you."

"I've probably heard worse."

"I'm an angel of The Lord."

Fury blinked. Then he narrowed his eyes. "I'm not playing games."

"Me neither." Castiel returned the stony gaze. "I'm telling the truth."

"There's no such things as angels."

"That's what a lot of people say." Castiel sat rigid. His eyes glowed bright blue and the outline of his large wings became outlined against the far wall. In a moment, they were gone.

"What the hell?!" Fury exclaimed, not believing what he was seeing. His mind was blown, to say the least. He'd never seen anything like it before. He had never believed in a higher power; it had never occurred to him that God actually existed, along with angels. Thor and Loki were both demi-gods, but they were aliens.

"So do you see now? This unholy abomination that's coming must be destroyed. I can help. You're going to need it," Castiel said.

Fury didn't say anything. He simply locked eyes with the angel and stared. The bright blue of Castiel's were like an ocean of wisdom.

"I see," was all Fury managed to choke out in the end.

"I can see you're troubled. Do not worry; I get this reaction a lot."

"So. . . you're here to help, you say?" Fury crossed his arms, finally regaining his senses. "Then we'll need to fill you in on the details."

* * *

"Well, since it's not Gabriel this time, though that's a relief, it shouldn't be that hard. I have my angel blade," Castiel said. He looked down at the hospital gown he was wearing- a white shirt and pants. "You do have my clothes, right?"

"I'm sure the staff kept them," Fury acknowledged, hands behind his back. "And we'll get you changed. Then I'll introduce you to the team."


	4. The Fight Begins

Castiel adjusted his tie. He'd never tied one before, but he'd delved into his vessel's brain and learned how. Within a moment, he was no longer bloody but clean and precise as always. He bounced his angel blade in his hand and then tucked it into his sleeve where it always stayed. Once that was done, the angel emerged from the changing room.

Director Fury stood waiting for him with Agent Romanoff. He nodded at Castiel. "Looking good. Now, let's introduce you to the team."

"That's here, anyways," Natasha added.

"Yes. I hear Thor and Banner are gone," Castiel said in his rather rough voice.

"Yes. Well, anyway. Come with us," Fury said.

Director Fury and Agent Romanoff led Castiel down a series of hallways and rooms. They ended up in a conference room. Three men sat at a glass table. They turned to look as the trio walked in.

"Team, this is Castiel," Fury introduced. Castiel nodded. "That's Tony Stark, Captain Steve Rogers, and Agent Barton." He pointed at each one as he named them off.

"And who is he? Why is he here?" Tony asked.

"Because he can help us."

"What can he do?" Steve asked. "He doesn't look very tough."

"I can do many things. A portion of them are probably unimportant to you, like when you pull my finger all lights go out," Castiel said.

"Ooh, I wanna see that," Clint said sarcastically.

"Do you? Why?"

"I was being sarcastic."

"Oh. I'm not very good with sarcasm. That's what many tell me."

"How come the lights go out?" Steve asked, one eyebrow cocked.

"I'm not sure why, really."

"I'm sorry, am I the only one who wants to see that?" Tony asked, standing up. He walked up to Castiel and nodded. "Stick out your finger."

Without a sound, Castiel stuck out his finger and Tony pulled on it. The lights immediately burst and the team was left shrouded in darkness.

"Well, that was certainly interesting," Natasha muttered. "Never thought I'd see that."

"Back to why this guy is here?" Steve prompted.

"He's got experience with fighting. He has something that might stop Loki," Fury said.

"Really? What?" Clint asked, leaning forward in his seat.

Castiel let the angel blade slip out of his sleeve. "This is an angel blade. It can kill anything."

"Angel blade? What the fuck does that mean, angel?"

"I am an angel of The Lord."

"You're an angel?" Rogers asked. He stood and walked over to Castiel. "For God?"

"Yes."

"God doesn't exist," Tony scoffed.

"Atheist, I presume. Don't worry, I don't kill them," Castiel assured. "One's religion is their own business. The Pagan gods are also worshipped. But most of them were murdered by Lucifer."

Clint rubbed the bridge of his nose. "What is this guy talking about? Angels? Gods? Fury, what are you thinking? This guy is insane."

Director Fury shot him a glare. "He has knowledge. And he's virtually unkillable."

"You can't kill him?" Tony asked, eyeing Castiel.

"Well, not exactly. You can hurt my vessel, but not my true form. To kill me, you'd need to hit my true form," Castiel informed.

"Vessel?" Steve questioned.

"Yes. This isn't me. My true form can be rather excruciating to humans. Many people have had their eyes melted and ears blown out from witnessing it."

"You're. . _inside_ someone?" Natasha muttered.

"Yes."

"So, a knife or gun wouldn't kill you? I can do this?" Clint asked, his bow drawn in an instant and an arrow cocked, being quickly fired. It hit Castiel right in the heart and stuck.

"No, that wouldn't work. I've been stabbed and shot. I've been killed and brought back by God himself. I don't think one measly little arrow will make a difference," Castiel said, gripping the shaft of the arrow and yanking it out. Blood dripped down his coat and the tip of the arrow. "And, for your information, I just cleaned myself off." He placed his hand on the wound and it vanished, blood, hole, and all.

"Holy shit," Stark breathed. "That's sick."

"But what can you do? Like, fighting wise?" Rogers asked.

"I can use my angel blade. I'm not good with guns," Castiel told them. "But I can also fly."

"Fly? Where're your wings?"

"You lesser beings can't see them. Only angels, demons, and other supernatural creatures can see them, including my true form."

"Lesser beings?!" Natasha scoffed. She placed her hands on her hips.

"Now, back to the task at hand. What's going on currently?" Castiel asked.

"We have to find Loki," Barton said.

Castiel closed his eyes. His eyebrows furrowed and his face contorted in concentration.

"Found him. He's in New York. Stark Tower, I think," Castiel informed as his eyes opened. Tony's own eyes went wide.

"Son of a bitch!" he exclaimed, already racing towards the door.

* * *

Castiel watched in stony silence as the remaining Avengers suited up and prepared themselves. As soon as they were about to go get on a jet, he stepped forward.

"I can get us to New York much faster," Castiel said.

"How?" Steve asked.

In an instant, the team was in New York. The humans jumped, staring around at the towering buildings. They looked to Castiel for answers.

"Sorry. I don't have all my juice yet. I figured here is as good as any," the angel said.

"That was fuckin' weird. . ." Tony muttered. He jumped into the air and zoomed off, a trail of smoke following.

* * *

Castiel waited on top of a building. He was watching for any signs of trouble, just as the Captain had told him to. He stood still as a statue, and one might have even mistaken him for one if his jacket hadn't been flapping in the breeze.

An explosion-like sound made the angel jump slightly. There, just across the city, Stark Tower was racked by an unearthly shaking, and a bright blue beam shot off the top, soaring into the sky. The area around the end seemingly collapsed in on itself, a large hole in the sky now forming.

From where he was, Castiel could see the small form of Iron Man shooting up the stream of blue, killing the things now pouring out. Castiel grimaced, feeling his insides twist and turn. The unholiness of this situation was going to take a horrible toll if it did not stop soon. Monster after monster emerged from the hole in the sky, passing Tony Stark and going into the streets. Castiel heard unimaginable noises in his head from the communication of the supposed 'mothership' to the creatures. He shut out the sounds and appeared down where the other half of the team was.

"Banner?" Captain asked, seemingly confused. He saw Castiel approaching and turned toward him.

Thor, he had seen. He'd dropped from the sky and conversed slightly with them before going after Loki. He returned after the portal opened, coming down the the ground.

"The powers surrounding the cube is impenetrable," Thor said grimly.

"Thor's right. We have to deal with these guys," Stark chimed, barely visible as he sped around killing aliens.

"So I take Banner is not here yet," Castiel said.

"No. But he'll be here."

"Uh, Cap, you might wanna have a look at this," Tony's voice sounded nervously from the mic. The team looked up and saw what was surely described as an abomination.

"Get it's attention," Steve ordered.

"Roger that."

It was long and worm-like, with soldiers spewing off from the sides. Mouths dropped around the group. Castiel paled, feeling his vessel's heart beat faster. He was visibly shaken and stumbled as his feet threatened to give out from under him.

"What?" Natasha asked, seeing him. "Are you okay?"

Castiel almost shook his head, but remained strong and just settled for a shaky nod. He swallowed, feeling some color return to his face.

Just as quick as the monster arrived, there was the rumbling of a motorcycle. They turned once again to witness Bruce Banner riding up. He stepped off the vehicle and slowly walked up to them.

"Well, this all seems. . horrible," he joked halfheartedly.

"I've seen worse," Agent Romanoff retorted, eyeing the scientist carefully.

"Sorry." He grimaced.

"No, it's fine. . . We could. . . use a little worse."

"Stark, we got him," Captain said.

"Banner?" came the reply.

"Just like you said."

"Then tell him to suit up. I'm bringing the party to you."

The beast in the sky roared and rammed into a building. Tony went soaring over and hovered in the air. The monster came down to the ground, destroying everything in its path.

"I-I don't see how that's a party," Romanoff muttered.

Banner glanced back at the team as he walked towards the thing.

"Doctor Banner, now might be a really good time for you to get angry," the Captain said. The beast neared.

"That's by secret, Captain," Bruce said, face straight, "I'm always angry." His clothes shredded as his body grew and turned green. He turned and smashed the leviathan in the face, crushing it as he was pushed back. It flipped over its own long body and landed behind them.

"Call it, Cap," Tony said as the team glanced around at the aliens.

The Captain quickly got into action. "Alright, listen up. Until we can close that portal up there, our biggest priority is containment. Barton, I want you on that roof, eyes on everything. Call out patterns and strays. Stark, you got the perimeter. Anything gets more than three blocks out, turn it back or turn it to ash."

Hawkeye turned to Tony. "Wanna give me a lift?"

Tony grabbed the back of his jacket. "Better clench up, Legolas." Iron Man shot off with Clint.

"Thor, you've gotta try and bottleneck that portal. Slow 'em down. You've got the lightning; light the bastards up." Thor nodded and swung his hammer, sending him flying upwards. The Captain quickly turned to Natasha. "You and me, we stay here on the ground, keep the fighting here." He looked over at Castiel. "Cas, you go wherever help is needed. You have that blade and your wings, so I'm not going to hold you back."

"Okay, got it," Castiel said. He waited as the Captain gave orders to the Hulk.

"And Hulk-"

He grinned.

"Smash."

Castiel vanished.

* * *

**Yes, I know it's not until season 6 that we found out whenever you pull Castiel's finger the lights explode, but that doesn't mean he didn't already know that. Besides, it's funny.**


	5. Angels, Demigods, and Sigils

**I had a whole chapter almost done. The whole chapter got deleted. This chapter would've been out like a week earlier. :| *rages internally* . . . *throws couch* . . . *throws several couches* **

**Fuck.**

* * *

Castiel appeared on a building. His whole body was shaking. Although, it was most likely caused by the huge beasts pouring out of the portal above Stark Tower.

Castiel furrowed his eyebrows and looked over at a load of passing Chitauri ships. The next moment, he was standing on the back of one. The creature started to hiss, but didn't get it out as Castiel's angel blade was forced into its abdomen. Black liquid spurted out and Castiel quickly stabbed the creature that served as the ship. As it was hitting the ground, he vanished, angel blade already a blur as several more ships were downed. The small platoon of Chitauri were gone, and Castiel wiped off his blade on the limp body of one.

"Castiel, there's a few of the bastards trying to get into the subway. We're busy over here; can you deal with them? I'm sure you can find it," the Captain's voice came scratchily from over the mic. Castiel squinted his eyes and, without even thinking, he was a block away. He saw the Chitauri. They were crowded around an entrance into the subway, but were being held off by a few policemen. It was obvious they needed help. A scream sounded from one of the cops and a crunching sound.

Castiel reappeared behind the Chitauri, angel blade ready. He grabbed one of the aliens and stabbed the weapon deep into its body. It fell with a strangled scream and went limp. The other creatures stopped attacking the police and turned to face the newcomer. They let out hisses and got their guns ready. A shot was fired into Castiel's shoulder, but it was unsuccessful in stopping his slow walk towards them. In a flurry of silver, the four remaining Chitauri were down and out. The cops looked, dumbfounded, at the angel. He blinked once and the next moment he was gone.

"It's taken care of," Castiel said into the mic.

"Heh, I knew it would. Continue with your work," Steve responded.

The angel watched some of the action going down around him. Iron Man zoomed past, a trail of Chitauri following closely behind. Narrowing his eyes, Castiel raised the angel blade. He threw it in one swift movement, the weapon sleek and steady as it soared towards its target. It lodged in the back of a 'living' ship and it went down with a screech, killing the riding alien as well. Castiel appeared down and retrieved his weapon from the bodies and rubble. He casually walked down the street, keeping an eye out for trouble.

Hulk emerged from a damaged building where a leviathan had obviously been taken down, as you could see its body hanging out. A few moments later, Thor stumbled out, gripping his hammer tightly in one hand and rubbing his head with the other. He grimaced and looked up, catching Castiel's eye. He grinned and walked towards him.

"Just the angel I wanted to see!" Thor exclaimed boisterously, pounding Castiel on his shoulder a few times, nearly knocking him to the ground.

"I'm the only angel you've ever knowingly seen," Castiel deadpanned.

Thor grinned. "Of course. I can see you and the Captain Steve Rogers would make very good acquaintances."

"Um. . . I guess."

"You know, except he does not have such amazing wings as yours. Or a halo." A hand came up and ruffled the pitch black feathers on Castiel's right wing, causing him to jump back and point the angel blade at the thunder God. Thor put his hands up, dropping Moujnir.

"Do not touch my wings," Castiel growled threateningly. The normally hidden-to-the-eye feathered appendages were flared down behind him, at a horizontal angle.

"I sincerely apologize. I did not mean to make you so uncomfortable. I just thought that since they're quite visible, things would touch them all the time," Thor said.

"They're not visible. To things that are not supernatural, I mean. They're not on the physical plane. They can't be touched or seen by anything that is only on the physical plane, such as humans." Castiel straightened himself up. "I did not know you could see them."

"Ah, I see."

"Yes. Which means. . . Loki will be able to see them too. And that's bad news. I won't be able to get close enough to kill him."

Thor's demeanor suddenly changed. He got up into Castiel's face threateningly, grabbing the lapels on his jacket. "You will _not_ touch Loki, understand me? He has done terrible things but he is still my brother. I love him too much for anything bad to happen to him."

Castiel shrank back slightly, the thunder god's sudden mood shift startling him a bit. "I understand. I will not harm Loki." He was then dropped rather crudely back onto the ground, as he had been pulled off his feet by Thor.

Thor sighed and rubbed his temple, his face showing turmoil. He turned towards Castiel one last time. "Let us go fight and forget this nonsense." Castiel nodded and disappeared.

* * *

Castiel pulled the blade out of the dead body with a sick sounding _schlick_ and looked around. Destruction and death surrounded him- but mostly dead bodies of the slain Chitauri. The portal was still not closed. He'd planned this from the start, and what had to be done had to be done. No matter what anyone said.

The angel directed his gaze onto the Stark Tower. In a moment, he was standing on the outside platform. He let the angel blade fall out of his sleeve, preparing himself for battle.

"My my my, so this is the angel the Chitauri have been chittering about. Well, they certainly didn't say we got such an attractive one," came a smooth voice from behind him.

Castiel spun around, facing the person. The black-haired man put his hands up in a sign of peace, grinning slyly as he glanced down.

"No need for alarm: wait, should there be? After all, I presume the only reason you'd come up here is to slay me, is it not?" Loki hummed, pacing the room.

Castiel narrowed his eyes and bounced his weapon in his hand a bit. "Close the portal or I'll use force."

Loki let out a small _tsk-tsk_ and shined his fingernails on his armor, taking a quick peek at them. "Really quite _boring_, angels, aren't they? The whole "surrender or you'll die" thing. Quite interesting."

"You're the one talking. Killing people if they don't bow down to you," Castiel growled.

"Technically, I said kneel," Loki corrected.

"Silence! I've heard enough! Close. The. Portal!"

"Hmmm. . ." Loki pretended to ponder this. "Nah."

"Then you leave me no choice." Castiel appeared right behind the god of mischief and swung his angel blade forward. Loki was quite fast, fortunately for him, and he quickly sidestepped and brought his scepter down on the angel's weapon, knocking it across the room, skidding across the floor.

Castiel growled and leapt back as the scepter came flying past his face. He rolled a bit and shot to his feet. The spear-like weapon came down on him again, courtesy of Loki, and Castiel grabbed it. He yanked fiercely on it, surprising the god, and brought him towards the angel. They both grabbed hold of it and became locked in battle, snarling right into each other's faces.

"Give up! You're nothing compared to me, foolish peasant!" Loki snapped, giving a sharp tug on the scepter. Castiel didn't release his grip and kicked at his opponent's legs.

"Really? I'm an angel, you ass," Castiel growled. He grunted as Loki head butted him with his golden horns.

"Yes, I'm aware. And I'm prepared. I didn't just sit on Earth doing nothing, you know." Loki smirked and gave a shove, knocking Castiel's legs out from under him at the same time. He yanked the scepter away and showed Castiel his hand, which was covered in blood. He slammed it down on the nearby counter, which contained an Angel Sigil. Castiel screamed in agony as a bright white illuminated the tower. As the light faded, the room was only filled with a smirking demigod.

* * *

Steve Rogers winced as he heard the horrible shriek and looked up at Stark Tower. Bright white light poured out the large windows on the side. Eyes wide, he glanced over at the agent accompanying him, Natasha Romanoff. She grimaced.

Steve began talking into his microphone. "Castiel? Castiel?" No reply, only static. The Captain grunted and tried a different tactic. "Stark? You there?"

". . Yep! You see that light?" came Tony's voice.

"Yeah, that's what I'm here for. Go over and check the building."

"On it."

Natasha turned around. "Captain, the bank on 42nd past Madison. They caught a lot of civilians there."

"I'm on it."

* * *

Tony landed in his tower, looking around. There was no sign of anyone, but there was something quite interesting scribbled on the countertop. Some kind of marking.

"Cap? I got something. It's a mark of some kind. It's written in blood too. Must have been Loki. He did something. I think he might've killed Cas," Tony said. There was a moment of silence.

". . Got it. Alright. We have to keep an eye out for Castiel, just in case. Hopefully he's not dead," Steve responded.

"I'll retake my eye in the sky."

* * *

**Hey, this actually turned out pretty good! _WAAAAYY_ different from the intended chapter, but I actually like this one better, though it's shorter than the original. And by the way,**

**CLIFFHANGER **

**HEHHE**

**But really, we all know Castiel isn't dead, right? **


	6. In the End it Matters

Castiel landed with a _thump _in the box of a pickup truck, his arms and legs splayed out. His head pounded dully for a moment before it faded away. He pushed himself onto his hands and knees.

God he hated those sigils.

The truck was speeding down the highway, not even noticing the new passenger in the vehicle. The celestial being fumbled for the edge of the box, trying to pull himself onto his feet. He managed to get onto his knees and that was all. There was static crackling in through the mic in his ear. The team was probably wondering what happened.

Castiel vanished, returning to the roof of Stark Tower. He fell to his knees as soon as he got there, still not able to stand up. The fighting seemed to have gotten worse. The portal was still not closed.

Castiel lay there for a good few minutes to regain his strength and then stood up, though rather shakily. He gripped the cement on the edge of the building, his legs threatening to give out from under him. As soon as he was ready, he blinked and was standing on the ground. He made his way past dented cars and destroyed building rubble to get to where he had last seen the Captain. He faintly saw a whipping of bright red hair, followed by a shriek from another life of a creature being ended.

The Black Widow leaned back against the ruined car, her breathing heavy. She tossed her hair back and closed her eyes for a brief moment. When she opened them, Castiel was standing in front of her, blood dripping down one side of his face.

"Castiel! You're alright!" she exclaimed, jumping up. "We thought maybe you had died!" She watched him stand there, in a trance-like state. She raised an eyebrow and snapped her fingers, trying to get his attention. He started, directing his gaze onto her.

"Are you okay?" Natasha asked, gripping his shoulders and giving him a shake.

"Yes, I'm fine. Sorry," Castiel said.

"You look pale. Maybe you should sit down." She tried to maneuver him to the hood of a car, but he pushed her off.

"I said I'm fine." He took a step forward but tripped slightly and caught ahold of a nearby chunk of concrete sticking out of the ground. Romanoff frowned and placed her hands on his shoulders.

"You're in a vessel, right? Which means that it's not your body. It's still human," she admonished gently.

"I've done much worse before," Castiel retorted sharply. He pulled away again. She sighed, rolling her eyes and then switched to her mic.

"Captain, we got Castiel. He's kinda. . . out if it," Natasha said.

There was a pause. "Out of it?"

"Yeah. . ." She trailed off as she watched the battered figure fall against a car. "He's a bit out of shape as of now. Can't really walk."

"I'll be right there."

In a matter of minutes, the Captain jumped up onto the edge of the road and strolled over to them, shield in hand.

"So, what happened?" he asked, eyeing Castiel warily.

"I'm not sure. Haven't asked yet," Natasha said.

"I'm just going to guess it had something to do with that symbol Stark found." They walked over to Castiel. "Are you okay?"

Castiel nodded carefully. "I'm fine. I just need to regain my strength."

"What happened?"

"Angel Sigil. They're used to send angels back to Heaven. Though it's painful, it's a good solution when there's an angel after you."

"And Loki used this to send you back to Heaven?" Romanoff inquired.

"Yes." Castiel nodded. "I was caught off guard. I didn't have enough time to stop him or ruin the sigil. As a result, I was forced rather rudely back to Heaven."

The Captain groaned and slammed his shield into the car, startling the two next to him. "Just great. Now that Loki knows he can stop Castiel, we'll never get close to him."

"I might not be able to stop him, but that doesn't mean-"

"What is it I hear of you trying to kill my brother?" a loud voice rumbled. Thor dropped out of the sky with a blast of thunder, smashing the cement under him. He stalked up to Castiel and took ahold of his lapels, similar to what he did earlier. He put his face right in the smaller man's and stared at him with the fiercest expression he could muster. "You attempted to kill my brother?"

Castiel furrowed his eyebrows. "I did what I had to do. The fate of the humans come first." His gaze grew misty. "Even over family."

Thor saw the look in his eyes and softened slightly, but continued glaring. "I said not to try and kill him. Look what he's gone and done to you." He shook the angel a bit.

"It's nothing." Castiel gripped Thor's wrists and tightened his hold, digging his fingers into his skin. Thor shifted uncomfortably but kept his hold. "I've had worse happen to me, and I've stayed standing and fighting. It was just a trip back to Heaven, was all. Not a big deal." He attempted to pry himself from the tight grip of the thunder god.

Thor snorted. "But I said for you not to try and kill my brother, and I meant it." He lifted Castiel off the ground and slammed him into the car before letting go. He backed up a few steps and launched himself off, hammer out in front of him.

Castiel grunted in pain and huffed, wiggling as to free himself of the metal twisted around his back. The Captain grabbed his arm and hauled him out of his half sitting position and onto his feet. There, the angel silently brushed himself off and stood still. He idly wiped the blood off the side of his face. It was proven futile, as the long cut stretched across his temple continued dripping down his cheek and around his eye, staining his eyebrow dark red.

The Captain sighed and rubbed his temple. "Uh, this horrible."

Natasha blew air out her nose. "It could be worse." An explosion sounded from above and a platoon of Chitauri flew around a corner.

Steve slowly shook his head. "What a cliché."

Castiel glanced around at the group. "I recommend we take action against the army now." He vanished into thin air and a moment later a few ships went down from above them. The team down on the ground faintly saw the outline of the angel moving rapidly between the ships, slaughtering the many aliens. Castiel reappeared not five minutes later, then wiped his blade on the inside of the destroyed car behind him.

The Captain eyed the angel for a moment before jumping into action. "Alright, get back to killing these things." He glanced around at the skies and then started off, jumping off the bridge. Castiel quickly vanished.

* * *

As time wore on, the Avengers were slowly beaten down. Thor and Captain America were down on the ground fighting, Hulk was being shot at by dozens of Chitauri, Hawkeye was laying in pain after having smashed through a window, and Iron Man was crumpled on the ground with aliens attacking him. Our poor friend Castiel was doing no better.

Laying on the roof of a building with a large stab wound through his side, Castiel weakly attempted to stand up. It didn't work very well.

That stupid creature. There had been so many, but he still should have been able to handle them very easily. Yet that one that slipped past the others and got its blade through him was killed fairly quickly after that. A strike with the Angel Blade had been far too much for it.

But yet, here Castiel was, weak and helpless on a rooftop, blood gushing out his side and rudely staining his suit and trench coat. He let his fingers trail up his side until it found the gaping hole. Within a moment, it was little more than a memory and he was able to stand up again. He brushed himself off.

As he did, Castiel saw Tony Stark whiz by, something large and seemingly deadly on his shoulders. The angel tilted his head, confused. His mic no longer worked so he had no idea what was going on and why. He glanced about and then appeared next to the Captain in a flutter of wings.

"What's happening?" Castiel asked roughly.

"Natasha can close the portal. But there's a bomb that needs to be rid of before. That's what Stark's doing," the Captain replied, eyes never leaving the sky. Castiel glanced up as well and saw the small shape of Tony get more distant. The portal swallowed him up.

Before their eyes, the remaining Chitauri collapsed, totally dead. Buildings buckled and crumbled under the weight of the fallen creatures.

"So we wait now?"

The Captain didn't reply right away, but waited a few moments. "Yes." Castiel frowned, but didn't say anything.

Minutes passed. Soon, Steve sighed. "Close it," he said into the mic. There was a sudden jerk in the energy keeping the portal open, and it began to close. But as it was nearly done, a small figure emerged from the hole. There was a laugh from the Captain. "Son of a gun."

Castiel tilted his head quizzically. "He's not flying."

Thor, who had been standing right next to them, started swinging his hammer. "He's not slowing down!"

Just as Tony fell to building level, Hulk emerged from nowhere, catching the falling man. They smashed into the ground. Hulk grunted and threw Stark off him, rolling back onto his feet. The team quickly made their ways over, Castiel being the first, as, you know, he flew.

The angel gripped the metal mask and ripped it off. He threw it behind him and looked at the man lying before him.

"Well?" the Captain asked.

Castiel didn't say anything. He very carefully pressed his fingers to Tony's forehead. With a gasp, the man burst into life.

"Holy hell!" Stark yelled, "what just happened?" He took a breath. "Please tell me nobody kissed me." Hulk roared. "Uh, did we win?"

The Captain grinned, looking around. "We won."

Thor looked grim. "Not yet."

* * *

Loki grunted as he pulled himself from the gaping hole in the floor. He managed to get himself onto the nearby stairs, sitting up. He suddenly froze. He glanced up.

Seven angry figures stood in front of him, glaring.

"If it's all the same to you," Loki started, putting his hands up, "I think I'll have that drink now."

Hulk snorted. Castiel glowered, face still dark with the dried blood. He angrily jabbed the angel blade in Loki's direction.

"You are the worst kind of person."

* * *

Castiel looked around. "The world is safe from aliens now, right?" They were back at SHIELD.

"For now," Fury responded cryptically.

"Well, I better be off then. Maybe I'll see you all again one day."

In a moment, the angel was gone.

Tony raised an eyebrow, taking a sip from his drink. "That guy does not know to say bye."

Natasha cast a glance at him. "Agreed."

* * *

Dean sat in a crappy hotel chair, watching the news. The alien attack in New York was horrible. Suddenly, Dean spit out his water, earning a yell from Sam.

"What the hell?" Sam snapped.

"Dude, dude, look!" Dean shouted, pointing at the television screen.

There, quite noticeably, was Castiel, killing alien after alien right next to Captain America. Sam felt his mouth drop open.

"Oh my god!"

"I know right! Castiel's a freakin' Avenger!"

"Not really. I just helped," came his voice from behind them.

"Holy hell!" Dean stammered, jumping around. "Is this what you were trying to warn us about?"

"Yes." He nodded. "And I ended up fighting." Dean turned to the tv again, in awe.

"Not much is known about the mystery fighter, but a bit of information was gained from the public. His name, currently dubbed as 'Castiel,' according to reports, was all that has been found out. Will we ever truly know who he is?" the reporter rambled on.

"Seems like they have your name, huh?" Sam grinned.

"Unfortunately, yes," Castiel grumbled. "I wish they didn't. I only fought because I didn't want the world to end."

"Well," Dean said, placing a hand on Castiel's shoulder, "you did a damn good job of stopping it."

* * *

**End! Hope you enjoyed! This story was one of my shortest. Hmm.**

**Ugh, endings are my worst features. **


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